Lions and tigers and bears, oh my. Yip Harburg, the lyricist for the 1939 film The Wizard of Oz, had it in mind to craft an entire song about the scary creatures that lay hiding in the woodlands of the witch-beset kingdom on the other side of Kansas, but he never landed on the right lines, settling instead on those seven words as a chant for the travelers to repeat as a way of keeping themselves safe in the forest.

Traditional hunters and human residents of ecosystems everywhere have given considerably more thought to the importance of those creatures and their moral equivalents—orcas and wolves here, dingoes and panthers there—and how humans can live with them. In 1927, when British biologist Charles Elton published his formulation of the food chain, he placed those large animals at the top of what he called the food chain, pointing to the flow of energy by which sun feeds grass feeds rabbit feeds fox.

Elton’s successors refer to these creatures as “apex predators.” Biostatisticians point to the fact that these creatures, at the top end of the chain, are few, in mathematical proportion to the animals that feed them: A million mayflies may go into the hundred trout that feed a single grizzly bear in a good bout of hunting.

Their relative fewness means that the apex predators carry a lot of weight, so to speak, in the workings of an ecosystem. Everywhere in the world, though, those apex predators have been supplanted by a single creature, Homo sapiens, and everywhere the world’s ecosystems are feeling the radical effects of this onset of what other scientists have come to call the Anthropocene: that time in which humans behave on the earth as if a geological force—or, worse, an extinction-causing asteroid.

A major survey paper, “Status and Ecological Effects?of the World’s Largest Carnivores,” written by a 14-member team of researchers and published in Science magazine in January 2014, examines the effects of this disappearance. In almost every part of the world, William Ripple and colleagues note, the last two centuries have brought the destruction of huge swaths of habitat, leading to the contraction of ranges and of prey. The food requirements of terrestrial apex predators often put them squarely in the sights of ranchers and other livestock producers, who consider bears, tigers, and other such animals to be threats to their livelihoods, while highways, cities, and suburbs interrupt migration paths.

Remove apex predators from the equation, and the world changes—and in ways that cannot easily be foreseen. Take foxes from the British edgelands, for instance, and suddenly you have an explosion of rodents, which in turn can mean an explosion in the transmittal of rodent-borne diseases to other animals and to humans; whence, for instance, the bubonic plague. Predator reduction has recently been having a pronounced role in the increased prevalence of zoonotic, or animal-borne, disease in Africa, a continent not well equipped to handle such health crises in the first place.

Fragmented forest–courtesy Stuart L. Pimm

Restricted habitat means that predator populations can become isolated, too, which appears to be the case with the wolves of Isle Royale, Minnesota; inbred, these wolves are falling victim to genetic disorders that reduce their numbers, while the population of moose, their erstwhile prey, grows, outstripping the ability of the land to support them. Everything from stream flow to crop production and even the number of wildflowers that pop up in spring turns in part on the work of these predators—all of which means, as the authors note, that “large carnivores and their habitats should be maintained and restored whenever possible.”

Indeed. And while that’s easier said than done, the International Union for Conservation of Nature (IUCN) has set forth an ambitious, comprehensive program of triage to rescue those species that can be rescued. The Iberian lynx, for instance, plays a critical role in the alpine ecosystems of the peninsula; while it remains Europe’s most threatened mammal, the cat has benefited from conservation efforts that have tripled its population in the province of Andalusia alone in the last decade. Just so, the Global Tiger Initiative has enlisted the governments of the 13 countries in which tigers live in the wild to provide a concerted program for conservation, including bans on poaching and the establishment of new preserves.

Cattle-free private land abutting the eastern edge of the Granite Mountain Open Allotment, near Jeffrey City, Wyoming–courtesy of Mike Hudak

In the end, little can be done to preserve apex predators without preserving great tracts of habitat. In Europe and North America, plenty of well-meaning and well-schooled scientists and their supporters are available to push through such far-reaching projects as the Wildlands Initiative. The project has helped identify and protect wildlife corridors by which the wolves of Yellowstone may one day be able to travel unimpeded all the way down to the Sierra Madre of Mexico, and vice versa, such genetic diversification being essential to the survival of Canis lupus. The situation is much different in the developing world, where a hungry and insistent human population is demanding that very habitat—and in the developing world, the authors of the report note, livestock production has tripled since 1980.

Areas without any livestock at all are of essential importance to the preservation of large carnivores, but that very notion swims against a vast historical tide. And although people everywhere are likely to agree in the abstract that large carnivores ought to be preserved as a moral imperative, it seems more likely that humans may one day soon live in a world in which those carnivores do not exist, or do not exist outside zoos. Fully three-quarters of all apex predator species, after all, are in rapid decline—and no evidence exists to suggest that life will be getting any better for them in the years to come.

"Service Animal" Scammers (New Yorker): An increasing number of your neighbors have been keeping company with their pets in human-only establishments simply by claiming that the creatures are their licensed companion animals and are necessary to their mental well-being.